Re: [PATCH risu] use time() as random seed and introduce --randseed option

[Peter Maydell <peter.maydell@linaro.org>]

On Fri, 5 May 2023 at 01:23, Jun Sun <jsun@junsun.net> wrote:
>
> Agree on the usefulness of generating the same test.  That is the reason behind adding --randseed option.  Once a seed is set, it always generates the same sequence of instructions.
>
> Basically with this patch,
>
> by default you will generate random instruction sequences for most testing cases
> you can provide a random seed option in the commandline to generate a deterministic instruction sequence
>
> Without this patch,
>
> we always get one fixed sequence (ie. random seed == 0 case)
> Otherwise we would have to manually modify code to generate random instruction sequences or generate a different fixed sequence.
>
> Hope this clarifies things a little bit.

Mmm; it comes down to: should we default to 'time' and
require the user to specify --randseed 0 to get the old
behaviour; or do we retain the current behaviour as the
default and let the user pass an option if they want a
non-reproducibly random output.

Alex, what do you reckon? You probably have been using
risugen more actively than me recently. I guess I vaguely
lean to "default to randomize(time)".

Also, should we make risugen print the random seed to stdout
so you can repro it even if you didn't pass --randseed initially?

Now that the random-seed-setting is 6 lines instead of 1,
this should definitely be abstracted out to a function
in the common code and not repeated in each per-arch file.

thanks
-- PMM